This invention relates to a combined gear-selector, sensor device for use with vehicle transmissions requiring precise, reliable sensing of the selected gear position for an extended period of time. This gear-selector, sensor device is particularly advantageous to vehicle transmissions utilizing a shift pattern having only gear positions which are: the home position; an upshift position; a downshift position; and a neutral position. Such a shift pattern, in contrast to the widely-used H-pattern, which requires extensive manipulation to achieve the desired gear position, has as an inherent advantage, an efficiency of operation which arises out of the reduced manipulation required in shifting to the desired gear position.
One gearshift position transmitter, using the above-described four-position pattern, can be found in the British Patent GB 2,107,279 which discloses that in the upshift and downshift positions, electronic logic independently selects the most suitable next higher or lower gear. This transmitter also provides that in the neutral position, the neutral gear is engaged and that the shift lever moves back to the home position by an elastic force after the selection of either the upshift or downshift position. Additionally, a gearshift preconditioning device, designed for the same type of transmission scheme, can be found in U.S. patent application Ser. No. 763,741, assigned to the assignee of the present invention. In this system, the neutral position within the vehicle transmission is preconditioned such that movement between the number of possible neutral gear positions is reduced. For the previously-mentioned disclosures, the electronic logic must recognize the current positions of the shift lever, preferably by means of a contactless sensing arrangement, so that wear of the sensing components does not affect the longevity of reliable operation. One such disclosure of a contactless sensing arrangement, found in U.S. Pat. No. 4,519,266 and assigned to the assignee of the present invention, is designed to apply to an H-shift pattern; and, accordingly, requires a complex arrangement of magnetic-field-sensitive sensors which are sampled according to a predetermined system operating sequence.
A further requirement of the gear-selector, sensor device is the transmission of operational requests in addition to the previously-detailed four gear positions that can be selected. Some service vehicles often have a split group of gears which is used to double the number of possible gear positions. Some types of activations can be provided on the gearshift lever to effect such an operational request for the split-position function. An example of such a gearshift lever, found in U.S. Pat. No. 4,380,938 and assigned to the assignee of the present invention, discloses a combined range valve and splitter valve formed as a part of the gearshift handle for accomplishing the multiple gear functions necessary for some service vehicles. Another advantageous feature of the gearshift lever is the provision of a second switch on the lever; which, at the initiation of the driver, instructs the electronic logic to skip one or more gears, thereby saving fuel in an empty or partly-loaded vehicle.
The electronic logic, which typically generates the ultimate control signals for the vehicle transmission once the request has been generated by the driver through manipulation of the gearshift lever, relies on operational sequencing in the form of instructions. One problem associated with such electronic logic arrangements has been the misinterpretation of one requested gear position for another through some fault in the sensor arrangement and/or transmission of the selected gear position.
It is also desirous of such gear-selector, sensor devices to be able to prevent a special gear function, such as, the gear-skip or split position operation, from being activated while in the neutral position. Additionally, selection of the neutral gear position once one of these special functions has been initiated, should not have an affect on the electronic logic arrangement, such as, cancellation of such request.